You need to know what lens mount your lens uses. As long as the mount is compatable with the camera, it should fit fine. If it's an old lens, you'll have to use the DSLR on manual exposure, since the old lenses don't have the electrical contacts to communicate with the body.

All Canon DSLRs use the Canon EF mount, which is the same mount that has been in use since the 80's, I think. Nikon DSLRs use the standard Nikon F mount, which has been in use for many decades.

You can use K Mount lenses on the Pentax *1st D. However, you will probably lose some features with older lenses and may have metering problems. It would not work on non-Pentax models.

If this is your only lens, I would not worry about trying to find a model that's compatible with it (50mm lenses are relativelyinexpensive for most models). Your description is a bit confusing, though (the "Auto Zoom" name implies that it's a zoom lens, versus a 50mm prime).

Also, you'll have a crop factor withmost DSLR models. Because their sensors are smaller than 35mm film, the entire image circle projected by the lens is not used. So, most models have a crop factor of around 1.5 (Nikon D70, D100) or 1.6 (Canon Digital Rebel, EOS-10D, EOS-20D).

In other words, a 50mm Lens would have a 35mm equivalent focal length of 75mm on most Nikon DSLR models (1.5 x 50 = 75mm) and a 35mm equivalent focal length of 80mm on most Canon DSLR models (1.6 x 50 = 80mm).

The Pentax *1st D also has a 1.5x crop factor (it's using a Sony CCD, similar to the one used in the Nikon D70).

yeah, i just posted the details on the lens to try and help identify it it does actually say the zoom thing.
thats good, thanks for the info. just wanted to see if i would have to buy two lenses, or just buy one. now ill buy two